William K. Gladding, SAMS® AMS® | Principal Marine Surveyor | (904) 945-0511 | bill@gladdingmarinesurvey.com

This is an outline for a DC electrical system designed for use on a small sailboat relying totally on battery power for weekend and holiday trips. It is a basic guideline that would be used to create more detailed specifications and was done free of charge (disclaimer) for its intended user.

AC system

  • 30 amp shore power inlet (adapter to plug in extension cord)
  • 30 amp shore power breaker
  • Xantrex Freedom HF 1800 Watt inverter/40 amp 12 volt charger (modified sine wave output)
  • Owner choice as far as numbers and locations of 115 volt convenience outlets or use outlets on inverter

DC system

  • Four Trojan T-125 six volt wet cell lead acid golf cart batteries or equivalent (total 480 amp hours)
  • Battery disconnect switch
  • Separate disconnect/slash breaker for inverter DC power supply
  • DC panel with appropriate number of breakers for intended loads


  • System based on =240 amp hour consumption for three days and two nights aboard without recharging batteries
  • Inverter/charger should allow recharging of batteries in approximately 120 to 240 minutes (depending on depth of discharge)
  • Lighting is the largest amp hour consumer calculations assume LED type bulbs for all lights
  • Inverter/charger is slightly more expensive than a comparable marine charger of the same output with the benefit of AC current when desired

References: ABYC E-11 (electrical standard) and Nigel Calders “Boat Owner’s Mechanical and Electrical Manual” Second Edition